An image reader is used to read image information recorded in a document, and can encompass a variety of devices including facsimiles, digital copiers, multi-functional devices, and other like devices.
An image reader can include a reading unit that radiates light to a document that is placed on a document glass or that is transferred through an automatic document feeder (ADF) to read image information from that document. The reading unit can include a light source and an image sensor to receive light reflected from the document and to convert the light into an electrical signal.
A document feeder generally includes a document inlet, through which the document that is to be read enters, a document outlet, through which the read document exits after being read, and a document transfer channel configured to transfer the document from the document inlet to the document outlet. The document transferred through the document transfer channel can pass over an ADF window arranged on the document transfer channel so that the image information recorded in the document can be read by the reading unit. The document transfer channel can be provided with a reference bar to support the document such that the document can be positioned close to the ADF window.
When the document feeder is used for a long time, the channel components of the document transfer channel, such as the ADF window or the reference bar, for example, can be undesirably abraded or contaminated. In these cases, problems such as non-uniform document transfer speed and vibration of transferred document may occur, resulting in a deterioration of the quality of image read.